In theory, each atomic node can be a Spaced Repetition card (this is essentially what I mean by atomic).

If it feels difficult to construct a spaced repetition card, it’s probably because that section of one’s knowledge graph is not yet broken down into atomic nodes with clear and simple connections to each other.

Any well-understood (i.e. chunked) node is defined by its relationship to other well-understood nodes, and one marker of a well-understood node is if it has a term or phrase it can be identified by. Using good Concept Handles might help when trying to flesh out an idea area.